# Electron Flow vs Conventional Current Flow - So Confusing!

#### nsaspook

Joined Aug 27, 2009
10,895
I'm afraid I may not be stating my question clearly enough. It's not necessarily the order of the components, but the order of the components relative to the actual electron flow. If electron flow is opposite conventional flow I'm having trouble understanding how current makes it's way around the circuit (for instance, without being blocked by a Diode that's in the circuit. I guess I'm thinking like a technician/troubleshooter would have to think?
Go with the flow. Think and use conventional flow notation unless it's necessary (unlikely with normal circuit theory) to understand the actual physics of the component.

#### WBahn

Joined Mar 31, 2012
28,163
I'm afraid I may not be stating my question clearly enough. It's not necessarily the order of the components, but the order of the components relative to the actual electron flow. If electron flow is opposite conventional flow I'm having trouble understanding how current makes it's way around the circuit (for instance, without being blocked by a Diode that's in the circuit. I guess I'm thinking like a technician/troubleshooter would have to think?
You are still trying to imagine that current can somehow "get" to one component in series without simultaneously "getting" to all of the components equally.

#### kubeek

Joined Sep 20, 2005
5,776
Seriously, the arrows are drawn in the conventional direction in transistors, also.
Just as a side note, that is only true with BJTs, MOSFETs have it the other way.

#### crutschow

Joined Mar 14, 2008
31,495
MOSFETs have it the other way.
The arrow in the typical MOSFET symbol shows the substrate connection, which is normally reverse-biased with respect to the drain terminal.

#### WBahn

Joined Mar 31, 2012
28,163
Just as a side note, that is only true with BJTs, MOSFETs have it the other way.

Uh... no.

There are a few different common MOSFET symbols, but all of them that have an arrow (and not all do) show the arrow going from the p-type material to the n-type material for the junction they are representing.

Please show an example where you think this is not the case (and perhaps I'm wrong).

#### kubeek

Joined Sep 20, 2005
5,776
Well yes, but for a common man who knows nothing about substrate or how fets are made, the arrow in an N-fet is pointing in the opposite direction of the arrow of an NPN.

#### WBahn

Joined Mar 31, 2012
28,163
Well yes, but for a common man who knows nothing about substrate or how fets are made, the arrow in an N-fet is pointing in the opposite direction of the arrow of an NPN.
Please show a picture of the symbol you have in mind.

Here are the most common ones that I'm familiar with (PFET on top, NFET on bottom)

The leftmost show the bulk connection internally connected to the source. Note that normally current flows between source and drain and that no current flows between the source and the middle of the channel. Thus you would not expect this diode to ever conduct.

The middle symbol is often used by "digital" circuit designers because it is cleaner and consistent with the switch-model and "bubble logic" mindset that most logic designers find useful.

The rightmost show simplified "analog" symbols often used for discrete device designs where it's understood (or ignored) that the bulk is source-connected. The bad thing about this symbol, even though it is nice and clean and makes visual comparisons between BJT and FET circuits easier, is that if you reverse bias the source-drain connection (based on the arrow direction) by more than a forward diode drop, you get current flow. That this is expected is readily apparent in the left-hand symbol.

For IC design work, the FETs are normally 4-terminal symbols with the bulk connection (the one with the arrow in the left-hand symbols), coming out as the fourth terminal instead of being shown as connected internally to the device source connection. There's generally no arrow or any other way to distinguish drain from source because the devices are symmetric and there is no distinction. Having the fourth terminal accessible independently is important because no only is the bulk not automatically connected to the source, but the bulk connections aren't even necessarily connected to each other.

#### ErnieM

Joined Apr 24, 2011
8,353
If you want people to understand you you need to speak a common language. In physics we have the International System of Units to define what "current" means. It is not defined in terms of electrons or protons or such. It is defined as charge passing thru a surface.

What most people miss is when you change the sign of the charge carrier at the same time you change the direction of the carrier you multiply a negative by a negative and achieve a positive current.

When you pretend current flows from negative to positive you reverse the sign of the current. That can have consequences when you are looking at other phenomena such as the magnetic field, which you will compute incorrectly by using electron flow instead of current.

Stop calling it "conventional" current. It is just current. Do something else and you are doing it wrong.

Period.

https://en.wikipedia.org/wiki/Electric_current

#### kubeek

Joined Sep 20, 2005
5,776
WBahn that is all true and nice and dandy, but for someone who barely understands what is going on in a bipolar transistor, saying that the arrow in all transistors points in the way of conventional current is at the least confusing., and that is what I wanted to point out.
An arrow pointing away from a bipolar transistor means it is an N(pn) transistor with current normally flowing from collector along the arrow into the emitter.
An arrow pointing away from a mosfet means it is a P(mosfet), and in that the current flows from source against the arrow into the the drain.
Forget that no current actually flows through the substrate, most people don´t even know there is such a thing as a substrate. The symbol of an N channel unipolar just looks like the opposite of an NPN bipolar.

#### Teljkon

Joined Jan 24, 2019
267
So for us noobs which side of a battery is a cathode which the anode or is there no correct answer.

#### jpanhalt

Joined Jan 18, 2008
11,087
I am rather fond of another prior explanation:
The anode is therefore that surface at which the electric current, according to our present expression, enters: it is the negative extremity of the decomposing body; is where oxygen, chlorine, acids, &c., are evolved; and is against or opposite the positive electrode. The cathode is that surface at which the current leaves the decomposing body, and is its positive extremity; the combustible bodies, metals, alkalies, and bases, are evolved there, and it is in contact with the negative electrode.The anode is therefore that surface at which the electric current, according to our present expression, enters: it is the negative extremity of the decomposing body; is where oxygen, chlorine, acids, &c., are evolved; and is against or opposite the positive electrode. The cathode is that surface at which the current leaves the decomposing body, and is its positive extremity; the combustible bodies, metals, alkalies, and bases, are evolved there, and it is in contact with the negative electrode.
Source:
Experimental Researches In Electricity.
Available online here: http://www.gutenberg.org/files/14986/14986-h/14986-h.htm

The term "anode" is used 73 time in that text, and there is no doubt that Faraday used the term to refer to the electrode at which "oxidation" occurred. Thus, it is relatively easy to keep straight for a battery producing power or any other electrochemical cell.

#### Norfindel

Joined Mar 6, 2008
326
Yeah, the symbols on the mosfets are somewhat confusing, but i relate the fact that the cathode of the arrow points to the center of the n channel mosfet, to the polarity of the channel. That helps.

#### Teljkon

Joined Jan 24, 2019
267